Compared to systemic administration, the simple and direct approach of topically applying a drug, such as an antibiotic, to the eye has several benefits, including the avoidance of side effects, bypassing the hepatic first pass, and reducing the likelihood of developing resistant strains of bacteria. However, for a variety of reasons, such as difficulty in delivering an effective amount of antibiotic to treat the infection, many antibiotics are not amenable or suitable for topical application to the eye or the tissue surrounding the eye, such as the eyelid.
U.S. Pat. No. 6,277,829 discloses a process for the preparation of an aqueous ophthalmic formulation containing azithromycin which comprises the ophthalmically acceptable polybasic phosphate, citric acid monohydrate, and azithromycin. However, these solutions which utilize phosphate buffer systems comprising phosphoric acid in combination with an external stabilizer, such as citric acid, can be irritating to the eye. Additionally, phosphate buffered system can promote fungus growth in the formulation.
As such there remains a need for stable concentrated yet well tolerated aqueous formulations of azalide antibiotics for topical application to the eye.
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